Method for conditioning well bores



Jan. 4, 1944. K. A. WRIGHT 2,338,372

METHOD FOR CONDITIONING WELL BORES Filed Aug. 19, 1939 Ei Z lll-W Patented Jan. 4, 1944 UNITED STATES PATENT vOFFICE 2,338,372 METHOD FOR CONDITIONINGIWELL BQRES Kenneth A. Wright, Los Angeles, Calif., assignor to B and W, Inc., Long Beach, Calif., a corporation of California Application August 19, 19.39, serial No. 291,027

(c1. iss-21) 8 Claims.

course of drilling the well. It is understood that when drilling a. well the drill bit is lowered into the well and rotated while drilling fluid is circulated downwardly through the bit and then upwardly within the well bore to the top of the well. II'his drilling fluid is a 4thin mud of a predetermined and controlled consistency and specific gravity. The drilling fluid serves the function of holding down fluid pressure within the well, carrying the cuttings to the surface of the well, and at the same time acts to mud or plaster up the walls of the well. It will be evident that the mud deposited on the well wall during the drilling operations will tend to retard the flow of fluid from the formation lwhen the well is put on production. When the casing is set in the well preparatory to production it is impossible to dislodge this material to place the well under optimum producing conditions. It is also common practice that after the Well bore has been finished a perforated or screen casing is set inthe well and is disposed in spaced relation to the wall of the well. In some instances the perforations may occur at denite points in the length of the well casing. In other instances the well casing is imperforate and provides'a lower end carrying a casing shoe through which circulation may be maintained. In either of the cases just referred to it will be evident that access to the wall surface of the open well bore cannot the wall of the well in the productive area or areas is abraded and cleaned with uid to expose the virgin earth formation immediately prior to the well going into production.

A further and important object of this invention is to provide a method of the character mentioned in which the production string or casing is utilized in the abrading and fluid circulating operations and is then utilized to conduct the well production fluid to the ground surface. This feature of multiple use or function of the single permanent production string saves the time,

`labor and expense that would of necessity be involved in assembling, running in, and removing a separate cleaning and flushing string and prevents the re-formation or re`depositing of a new mud cake on` the wall of the well bore during the interval of time that would be required for such separate abrading and flushing operations.

The invention` is illustrated by way of example in the accompanying drawing, in which:

Figure 1 is a more or less diagrammatic view in central vertical section and elevation disclosing the manner of employing the method of the present invention when a perforated section of well casing is to be set in a well.

Fig. 2 is a view similar to Fig. 1 in vertical secl tion and elevation showing a well and a section be gained by means of tools after the casing has i been set in position.

thereon during the drilling operations.

Another object of this invention is to provide a method of the character mentioned in which of casing disposed therein with the abrading members appearing on an imperforated casing.

Fig. 3 is a transverse section through the structure as seen on the line 3-3 of Fig. 1.

The method of the present invention may be said to comprise, generally, the following steps or operations, the drilling'of a well; providing abrading means on a production string or cas ing; lowering the casing into the well; manipulating the casing so that the abrading means abrades the wall of the well in and adjacent productive area or areas of the well bore, circulating fluid through the same casing and the well during the abrading operation to flush out the ma-I terial abraded from the well Wall and to prevent the reformationof a mud cake on the well Wall, and then causing or allowing the well fluid from the earth formation to produce or flow out of the well through the self same string or casing.

Referringmore particularly to the drawing, I0 indicates the normal wall surface of a well bore Il. Deposited upon this wall surface is a thickness of mud or `.the like I2 as is usually formed during the well drilling operations. Extending downwardly into the well bore II is the usual production string or well casing I3. As shown in Fig. 1 of the drawing a perforated well screen In accordance with the method of the inventionV the wall of the well bore is abraded and cleaned before setting the casing. For this purpose I provide brush elements I1. These elements are secured to the sections of the screen at longitudinally spaced points by backing rings IB and project radially therefrom. The bristles of the brushes are preferably made of stiil' steel wire. The brushes I1 are formed so that when the lower casing section I4 is introduced into the well bore to a level adjacent that to which it is to be set the bristles of the brushes will project outwardly against the wall in position to abrade and scour the same. The casing or production string and the lower section I4 may then be reciprocated within the well bore so that the wall surface III is completely scoured by the brushes. This will act to remove the deposit of mud indicated at I2 and will clean and open up or expose the virgin formation of the wall surface- I oi' the well bore II. Fluid is pumped or passed down through the wash pipe to carry away the mate rial freed or loosened bythe brushes` and to pre-4 vent the re-forming of the mud cake to insure that the area of the well bore from which the iluil yield is expelled from the formation will be completely opened up to permit the fluid to flow copiously. A partition 30 is arranged across the upper end of the well screen Il, and removably passes or receives the wash pipe I B, to prevent the return flow of the fluid through the casing I3.

In the form of the invention shown in Fig. 2 of the drawing the brushes I1 are shown mounted upon an imperforate length of well casing in which instance the abrasive action of the brushes will be the same as previously described and may be used to scour and condition the surface of the well bore at any point throughout the length thereof.

In carrying out the method of the present invention the well is drilled by usual methods employed in rotary well drilling, during which time the mud-laden drilling uid circulates downwardly through the drill string, outwardly through the eyes of the bit, and upwardly along the wall surface I0 ofthe well bore II. As this operation proceeds it is usual for a thickness or coating of mud I2 to be deposited on the wall surface. When it is desired to set the final casing and a perforated string for production the casing section I3 is lowered on the bottom of the string of casing and may be perforate or imperforate as desired. In any event the brushes I1 are mounted on the screen I3 and so that their bristles engage the wall of the bore to abrade the same. When the casing section I3 has reached substantially the proper position for setting the production string or casing may be moved up and down in the hole and rotated if desired so that the wall may be completely scoured and extraneous matter removed therefrom. The wash pipe T6 is connected to a source of fluid under pressure so that during this movementl iiuid may bel forced downwardly and outwardly assas'ra through the end of the casing shoe I5 and into the well bore to thereafter rise within the well bore and remove the freed mud-cake of extraneous material from within the well. The well is then in condition for production and the casing I3 may then be set while the brushes remain in position.

It will thus be seen that by this method of conditioning a well a final step in treating the wall of the well is carried on after the casing has vbeen placed within the well, thus insuring that the producing area of the well will be placed in the best possible condition for efilcient flow f fluid from the formation.

While I have shown the preferred method oi conditioning a well bore it will be understood that various changes might be made in the steps of themethod by those skilled in the art without departing from the spirit of the invention as claimed.

Having thus described my invention, what l claim and desire to secure by Letters Patent is:

l. 'I'he method herein described comprising drilling a well with the rotary method in which mud laden fluid is circulated through the well to form a mud cake on the wall thereof, providing a tubular production string with external abrad- -ing means positioned to be in a given zone of the well when the string has been located in the well, running said string into the well to bring the abrading means into said zone, manipulating said string to cause said abrading means to abrade the mud cake from the wall of said zone of the well, circulating fluid through said string and the well during said abrading of the well wall to carry away the freed mud cake and to prevent the re-depositing of a cake on the well wall, and then causing the iluids from the earth formation which has been exposed by said abrading to flow from the well into said string.

2. The method herein described comprising drilling a well with the rotary method in which mud laden fluid is circulated through the well to form a mud cake on the wall thereof, providing a tubular production string with external abrading means, running said string into the well, manipulating said string so that the abrading means thereon abrades the mud cake from a portion of the well wall to expose the earth formation, circulating fluid through said string and the well during said abrading to carry away the freed mud cake, and then utilizing said string to conduct away the fluid yield from the earth formation exposed by said abrading action.

3. The method of preparing a well for production comprising providing a tubular production string with abrading means, lowering said string into the well, manipulating said string to cause --said abrading means to abrade the wall of `a portion of the Well and thus expose the virgin earth formation, and then utilizing the self same string to conduct the fluid yield from the earth formation, thus exposed.

4. Ihe method of preparing a well, which has a productive area, for production, comprising providing a tubular production string with external abrading means in a position to be in said area when the string is located in the well, lowering said string into the well to bring the abrading means into said area, abrading the wall of the well in said area by manipulating said string so that the abrading means acts on the well wall, and then utilizing said lstring to conduct the fluid yield from said area.

5. The method of preparing a well for production comprising providing a tubular production string with abrading means, lowering said string into the well, manipulating said string to cause said abrading means to abrade the wall of a portion of the well and thus expose the virgin earth formation, circulating fluid through the string and well during said manipulation of the string to carry away the material abraded from the well wall by said means, and then conducting the fluid yield from the earth formation through said string.

6. The method of preparing a well for production comprising providing a well screen with external abrading means, lowering the screen into the well on a tubular string, manipulating the string to cause said abrading means to abrade the wall of the well and expose Lthe virgin formation thereof, conducting uid downwardly through said string and screen for discharge into the well during said manipulation of the string to flow upwardly in the well and maintain said exposed formation free and clean, and then conducting the fluid yield from said exposed formation into the screen and through said string.

7. The method of preparing a well for production comprising providing a tubular production string with abrading means, lowering said string into the well, manipulating said string to cause said abrading means to abrade the wall of a portion of the well and thus expose the virgin earth formation, and then setting the string to form aconduit for carrying away the fluid yield.

8. The method of preparing a well for production comprising providing a perforate well screen with external abrading means and an internal wash pipe, lowering the screen into the well, manipulating the screen so that said means abrades the wall of the well, circulating uid downwardly through the wash pipe and upwardly through the well during said manipulation to wash away the material abraded free by said means, and then withdrawing the wash pipe from the well leaving the perforate well screen in place in the well.

KENNETH A. WRIGHT. 

